1 files changed, 62 insertions, 0 deletions
diff --git a/appl/wm/mpeg/remap4.b b/appl/wm/mpeg/remap4.b
new file mode 100644
index 00000000..20566fc2
--- /dev/null
+++ b/appl/wm/mpeg/remap4.b
@@ -0,0 +1,62 @@
+implement Remap;
+
+include "sys.m";
+include "mpegio.m";
+
+Mpegi, YCbCr: import Mpegio;
+
+CLOFF: con 255;
+
+width, height, w2: int;
+out: array of byte;
+elum: array of int;
+clamp16 := array[CLOFF + 256 + CLOFF] of int;
+
+init(m: ref Mpegi)
+{
+	width = m.width;
+	height = m.height;
+	w2 = width >> 1;
+	out = array[w2 * height] of byte;
+	elum = array[width + 1] of int;
+	for (i := 0; i < CLOFF; i++)
+		clamp16[i] = 0;
+	for (i = 0; i < 256; i++)
+		clamp16[i + CLOFF] = i >> 4;
+	for (i = CLOFF + 256; i < CLOFF + 256 + CLOFF; i++)
+		clamp16[i] = 255 >> 4;
+}
+
+remap(p: ref Mpegio->YCbCr): array of byte
+{
+	Y := p.Y;
+	for (e := 0; e <= width; e++)
+		elum[e] = 0;
+	m := 0;
+	n := 0;
+	for (i := 0; i < height; i++) {
+		el := 0;
+		ex := 0;
+		for (k := 0; k < w2; k++) {
+			y := (256 - int Y[n++]) + elum[ex];
+			l := clamp16[y + CLOFF] << 4;
+			b := l;
+			y -= l;
+			t := (3 * y) >> 4;
+			elum[ex] = t + el;
+			elum[ex + 1] += t;
+			el = y - 3 * t;
+			ex++;
+			y = (256 - int Y[n++]) + elum[ex];
+			l = clamp16[y + CLOFF];
+			out[m++] = byte (b | l);
+			y -= l << 4;
+			t = (3 * y) >> 4;
+			elum[ex] = t + el;
+			elum[ex + 1] += t;
+			el = y - 3 * t;
+			ex++;
+		}
+	}
+	return out;
+}